Hands-free, sometimes referred to as touch-free, dispensers are well known in the art. Many of these dispensers are battery powered which allow them to be conveniently placed most anywhere without connection to electrical service. Of course, batteries, also referred to as cells, run down over a period of time and this requires that the batteries be replaced. If a battery is not timely replaced then the dispenser is rendered inoperative. One way to overcome this problem is to replace the battery on a predetermined schedule. However, this is considered wasteful as the full life of the replaced battery is not used.
In the context of hands-free dispensers, it has been determined that a user sensor preferably responds within 200 milliseconds upon detection of a target and dispenses a fluid such as a soap. This requires that the user sensor wake and detect a target at least four times per second. However, user sensors that detect slower events, like flush valves, respond in one second or more to a target. This allows for a lower duty cycle and thus lower power consumption. This same lower duty cycle can be used with a soap dispenser; however, skilled artisans will appreciate that this results in lost opportunities to provide soap to a user. In other words, users frequently like to receive a second dispensing of soap prior to exposing their hands to water and washing their hands. Additionally, it has been found that a user prefers to receive a second dose of soap more quickly than the first.
Current devices that provide for fluid soap dispensing utilize the same duty cycle whether the dispensing device is busy or not. Accordingly, more electrical power is used even though the dispenser may not be utilized for significant periods of time. Indeed, a particular prior art fluid dispenser, such as one that uses an infrared detection sensor, utilizes ten thousand times more current when it is on, than when it is off. In any event, some washrooms or restrooms only see extended or busy activity during weekends and are dormant during the rest of the week. Additionally, some dispensers may be more busy during certain periods of the year such as summertime in park-like settings and not busy during the wintertime. Moreover, skilled artisans will appreciate that the duty cycle determines the response time for when the user places their hand underneath the infrared sensor. Moreover, when the sensor is not in use, it is necessary to keep the sensor on in some type of duty cycle to keep the sensor calibrated to the ambient environment. Although some prior devices acknowledge the need for turning on a sensor or turning off a sensor, there is little appreciation as for the need to maintain calibration of the sensor. Therefore, there is a need to extend battery life for hands-free dispensers. Moreover, there is a need for the ability to adjust a duty cycle to reduce power consumption during non-use of the dispenser and to increase duty cycle during periods of extended use.